Korea, US should move past cost sharing squabbleA just-concluded defense cost sharing deal between South Korea and the United States calls on Seoul to pay 1.04 trillion won ($923 million) this year for the upkeep of U.S. troops stationed here, up 8.2 percent from last year.The deal means the host country must pay a greater contribution to maintain the 28,500-strong U.S. Forces Korea (USFK). The increase rate is the highest since Korea began to share the costs in 1991. Seoul officials said the amount is down from a last-minute U.S. demand for $1 billion. However, the growth rate is much higher than last year's inflation rate of 1.5 percent.The Moon Jae-in government said it has done its best not to give in to excessive U.S. requests. Washington once demanded Seoul pay as much as $1.2 billion for the operation of the USFK. President Donald Trump even wanted Korea to pay 100 percent of the cost.There is another worry for Korea: the one-year contract term of the so-called Special Measures Agreement or SMA. Seoul wanted the deal to be valid for three to five years as in previous agreements. But the U.S. succeeded in making the period only one year, saying Washington was still extensively reviewing cost sharing agreements with other allies.The problem is that Seoul will soon have to start negotiations for the SMA for next year. It is also burdensome to undergo the hectic negotiations every year. So Korea needs to demand the U.S. accept its multi-year formula.Officials argue that the country made a concession in terms of the contract period, while managing to contain its payment ceiling below the $1 billion mark. But they have to admit that the U.S. will no doubt pressure Seoul to pay more ― probably much more than ever.In this context, we have to ask: What is the U.S.-Korea defense alliance for? The traditional alliance has so far been mutually beneficial. However, it is doubtful if the alliance can be sustainable if Washington continues to force Seoul to shoulder a greater burden. This is all the more so because President Trump harbors a misguided perception that South Korea is a "free rider" in the bilateral defense alliance. Trump must have regarded the alliance as a means to maximize its economic benefits at the sacrifice of the Asian ally. It may be natural for the real estate tycoon-turned-president to approach the alliance from a financial perspective. The Trump administration even insinuated that the U.S. might cut or withdraw its troops from Korea if we refuse to contribute more for the upkeep of the USFK. This has raised concerns among Koreans who cannot totally rule out the possibility of a troop pullout or cutback amid the ongoing denuclearization talks between Washington and Pyongyang.Trump's unilateralism and his "America first" policy could run the risk of undermining the Korea-U.S. alliance. To prevent this risk and strengthen the alliance, the two countries should value the strategic importance of the alliance in the region more than its financial cost.